In the life science field, preparation of recombinant proteins is widely performed as a part of basic research, applied research and product development. For detection and purification of recombinant proteins expressed in Escherichia coli or animal cells, adding a tag, i.e., a peptide of several residues, to the terminus of an objective protein is usually performed. However, since the tag is considered to affect the bioactivity, the crystal structure and the like of the objective protein, the tag must be ultimately separated off. Therefore, it is necessary to insert a specific protease recognition sequence between the tag and the objective protein.
For example, Non Patent Literature 1 describes a complex tag composed of a histidine tag in combination with an MBP (maltose binding protein) tag and a Tobacco etch virus (hereinafter referred to as “TEV”) protease recognition sequence. Non Patent Literature 2 also describes a complex tag composed of protein A in combination with calmodulin binding peptide (CBP) and a TEV protease recognition sequence. However, in each of the above literature, the TEV protease recognition sequence is used only for separation of the added tag, and is not used per se as a tag for detection and purification. Use of a protease recognition sequence per se as a tag for detection and purification is expected to greatly simplify the design of the construct.